The present invention relates to a slotting method in which, during production of a metal sheet V-pulley, a metal sheet brake shoe, or the like, an outer peripheral portion of a blank is split into two parts in the thickness direction, a slotting device, and a method of manufacturing a metal sheet brake shoe by slotting.
As a slotting method in which, during production of a metal sheet V-pulley, an outer peripheral portion of a disk-like blank is split into two parts in the thickness direction, for example, a slotting method is disclosed in Japanese Patent No. 2520095. In the slotting method, the outer peripheral portion of a disk-like metal blank is slit in the thickness direction into two parts by a slotting roller die. In the slotting roller die used in the method, an edge-like blade portion is protruded in the circumferential direction in an axial center portion of the outer peripheral face. While pressing the edge-like blade portion against a center portion in the thickness direction of the outer peripheral face of the blank, the slotting roller die and the blank are synchronously rotated, whereby the outer peripheral portion of the blank is slit into two parts in the thickness direction.
In the above-mentioned slotting method, the edge of the blade portion of the slotting roller die easily slips over the outer peripheral face of the blank in the thickness direction during an initial stage of the slotting process, and hence it is not easy to slot the outer peripheral face of the blank at an arbitrary position in the thickness direction. In the case where a thin blank is used, particularly, instability and difficulty of centering and equal slitting in the process of slotting a center portion in the thickness direction of the outer peripheral face of the blank are conspicuous.
It is an object of the invention to provide a slotting method in which slitting can be correctly easily performed at an arbitrary position in the thickness direction of an outer peripheral face of a blank, a slotting device for the method, and a method of manufacturing a metal sheet brake shoe by slotting.
The slotting method of the invention is a slotting method in which a disk-like metal blank is clampingly held between upper and lower rotary dies, a slotting roller die is pressed against an outer peripheral portion of the blank, and the outer peripheral portion of the blank is split into two parts in a thickness direction, wherein a blank housing recess a depth of which is smaller than a thickness of the blank is formed in an upper face of the lower rotary die on which the blank is to be placed, a roller die guiding face is formed horizontally and continuously with an outer periphery of an upper end of an outer peripheral wall of the blank housing recess to be lower in level than an upper face of the blank in the blank housing recess, the upper rotary die is formed to have an outer diameter which is smaller than an outer diameter of the lower rotary die, thereby allowing an upper face of the outer peripheral portion of the blank in the blank housing recess to be exposed, the slotting roller die has a blade edge on an outer periphery of the die, and, while the slotting roller die is rotated in synchronization with the blank about a roller axis which is inclined with respect to a rotation axis of the upper and lower rotary dies, the blade edge is slid on the roller die guiding face in an inward radial direction to be pressed against the outer peripheral portion of the blank which is protruded from the blank housing recess, whereby the outer peripheral portion is slit into two parts in the thickness direction.
According to this method, slotting can be surely performed at a position (slotting position) which is in the outer peripheral portion of the blank protruded from the blank housing recess of the lower rotary die, and which coincides with the level of the roller die guiding face, without causing a positional displacement by the blade edge of the slotting roller die which is slid along the roller die guiding face. When the outer peripheral portion of the blank is to be slit into two parts of the same thickness in the thickness direction, for example, the center portion in the thickness direction of the outer peripheral portion of the blank can be therefore surely slotted simply by housing the blank in the blank housing recess so that only a portion of a half of the thickness of the blank is protruded. Namely, when the blank is housed in the blank housing recess so that a desired slotting position of the outer peripheral portion of the blank corresponds to the level of the roller die guiding face, slitting can be performed correctly and easily at an arbitrary position in the thickness direction of the outer peripheral portion of the blank. Under a state where the whole of the blank including an outer peripheral portion is supported in the housing recess of the lower rotary die, the outer peripheral portion of the blank can be slotted stably and surely. Therefore, the method is optimum for slotting an outer peripheral portion of a blank of a reduced thickness.
In the slotting method of the other invention, after an outer peripheral portion of a blank which is protruded from a blank housing recess of a lower rotary die is slotted into two parts in a thickness direction to form upper and lower slotted parts by a blade edge of a slotting roller die in the same manner as the above-mentioned slotting method, the blank is further clampingly held between second upper and lower rotary dies so that the upper and lower slotted parts are outward protruded from outer peripheral faces of the upper and lower rotary dies, and an expanding blade portion of an expandingly forming roller die is pressed against the slotted parts, the expanding blade portion being formed on an outer peripheral face in a circumferential direction, to straight expand the slotted parts in upward and downward directions.
According to this method, it is possible to easily produce a slotted product of a shape having: a web which is configured by a part of the blank that is clamped between the second upper and lower rotary dies; and rims which are configured respectively by the slotted parts that are formed continuously with an outer peripheral portion of the web.
The slotting device of the other invention is a slotting device comprising: upper and lower rotary dies which clampingly hold a disk-like metal blank; and a slotting roller die which, while being rotated in synchronization with the blank, presses a blade edge against an outer peripheral portion of the blank to slit the outer peripheral portion into two parts in a thickness direction, wherein a blank housing recess a depth of which is smaller than a thickness of the blank is formed in an upper face of the lower rotary die on which the blank is to be placed, a roller die guiding face is formed horizontally and continuously with an outer periphery of an upper end of an outer peripheral wall of the blank housing recess to be lower in level than an upper face of the blank in the blank housing recess, the upper rotary die is formed to have an outer diameter which is smaller than an outer diameter of the lower rotary die, to allow an upper face of the outer peripheral portion of the blank in the blank housing recess to be exposed, the slotting roller die has a blade edge on an outer periphery of the die, and, while the slotting roller die is rotated in synchronization with the blank about a roller axis which is inclined with respect to a rotation axis of the upper and lower rotary dies, the blade edge is slid on the roller die guiding face in an inward radial direction to be pressed against the outer peripheral portion of the blank which is protruded from the blank housing recess.
As a result of the use of the device, when the blank is housed in the blank housing recess so that a desired slotting position of the outer peripheral portion of the blank corresponds to the level of the roller die guiding face, slitting can be performed correctly at an arbitrary position in the thickness direction of the outer peripheral portion of the blank.
Furthermore, the method of manufacturing a metal sheet brake shoe of the other invention is a method of, by using a disk-like metal blank, manufacturing a metal sheet brake shoe having a shoe rim which has a partially arcuate shape, and a shoe rib which is protruded from an inner periphery of the shoe rim, and includes: the slotting step of splitting an outer peripheral portion of the blank which is protruded from a blank housing recess of a lower rotary die, by a blade edge of a slotting roller die into two parts in a thickness direction to form upper and lower slotted parts; an expandingly forming step in which the blank is clampingly held between second upper and lower rotary dies so that the upper and lower slotted parts are outward protruded from outer peripheral faces of the upper and lower rotary dies, and an expanding blade portion of an expandingly forming roller die is pressed against the slotted parts, the expanding blade portion being formed on an outer peripheral face in a circumferential direction, to straight expand the slotted parts in upward and downward directions, thereby shaping a web which is configured by a part of the blank clamped between the upper and lower rotary dies, and rims which are configured respectively by the slotted parts that annularly expand toward both sides in a thickness direction of an outer peripheral portion of the web; and a step of cutting the web and the rims into a required shape, thereby forming a brake shoe having a shoe rim which has a partially arcuate shape, and a shoe rib which is protruded from an inner periphery of the shoe rim.
According to the method, a metal sheet brake shoe having a shoe rim which has a partially arcuate shape, and a shoe rib which is protruded from an inner periphery of the shoe rim can be easily produced from a disk-like metal blank.